maximize azimuthal acceptance

compact/drich.xml

@@ -148,7 +148,7 @@
   backplane="DRICH_window_thickness + 5.0*cm"
   rmin="DRICH_rmin1 + DRICH_wall_thickness + 0.0*cm"
   rmax="DRICH_rmax2 - DRICH_wall_thickness - 2.0*cm"
-  phiw="53*degree"
+  phiw="59.5*degree"
   thickness="0.2*cm"
   focus_tune_long="0.5"
   focus_tune_perp="0.2"

src/DRich_geo.cpp

@@ -4,7 +4,7 @@
 //
 // Author: Christopher Dilks (Duke University)
 //
-// - Design Adapted from Standalone Fun4all and GEMC implementations 
+// - Design Adapted from Standalone Fun4all and GEMC implementations
 //   [ Evaristo Cisbani, Cristiano Fanelli, Alessio Del Dotto, et al. ]
 //
 //==========================================================================
@@ -121,7 +121,7 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
   /* - `vessel`: aluminum enclosure, the mother volume of the dRICh
    * - `gasvol`: gas volume, which fills `vessel`; all other volumes defined below
    *   are children of `gasvol`
-   * - the dRICh vessel geometry has two regions: the snout refers to the conic region 
+   * - the dRICh vessel geometry has two regions: the snout refers to the conic region
    *   in the front, housing the aerogel, while the tank refers to the cylindrical
    *   region, housing the rest of the detector components
    */
@@ -201,7 +201,7 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
   // reference positions
   // - the vessel is created such that the center of the cylindrical tank volume
   //   coincides with the origin; this is called the "origin position" of the vessel
-  // - when the vessel (and its children volumes) is placed, it is translated in 
+  // - when the vessel (and its children volumes) is placed, it is translated in
   //   the z-direction to be in the proper ATHENA-integration location
   // - these reference positions are for the frontplane and backplane of the vessel,
   //   with respect to the vessel origin position
@@ -307,13 +307,13 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
     int imod=0;
 
     // thetaGen loop: iterate less than "0.5 circumference / sensor size" times
-    double nTheta = M_PI*sensorSphRadius / (sensorSide+sensorGap); 
+    double nTheta = M_PI*sensorSphRadius / (sensorSide+sensorGap);
     for(int t=0; t<(int)(nTheta+0.5); t++) {
       double thetaGen = t/((double)nTheta) * M_PI;
 
       // phiGen loop: iterate less than "circumference at this latitude / sensor size" times
-      double nPhi = 2*M_PI * sensorSphRadius * std::sin(thetaGen) / (sensorSide+sensorGap); 
-      for(int p=0; p<(int)(nPhi+0.5); p++) { 
+      double nPhi = 2*M_PI * sensorSphRadius * std::sin(thetaGen) / (sensorSide+sensorGap);
+      for(int p=0; p<(int)(nPhi+0.5); p++) {
         double phiGen = p/((double)nPhi) * 2*M_PI - M_PI; // shift to [-pi,pi]
 
         // determine global phi and theta
@@ -337,7 +337,7 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
         double phiCheck = std::atan2(yCheck,xCheck);
 
         // patch cut
-        bool patchCut = 
+        bool patchCut =
           std::fabs(phiCheck) < sensorSphPatchPhiw
           && zCheck > sensorSphPatchZmin
           && rCheck > sensorSphPatchRmin
@@ -419,7 +419,7 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
 
     // focus 2: move focal region along sensor sphere radius, according to `focusTuneLong`
     // - specifically, along the radial line which passes through the approximate centroid
-    //   of the sensor region `(sensorCentroidZ,sensorCentroidX)` 
+    //   of the sensor region `(sensorCentroidZ,sensorCentroidX)`
     // - `focusTuneLong` is the distance to move, given as a fraction of `sensorSphRadius`
     // - `focusTuneLong==0` means `(zF,xF)==(zS,xS)`
     // - `focusTuneLong==1` means `(zF,xF)` will be on the sensor sphere, near the centroid
@@ -460,29 +460,40 @@ static Ref_t createDetector(Detector& desc, xml::Handle_t handle, SensitiveDetec
     // if debugging, draw full sphere
     if(debug_mirror) { mirrorTheta1=0; mirrorTheta2=M_PI; /*mirrorPhiw=2*M_PI;*/ };
 
-    // solid and volume: create sphere at origin, with specified angular limits
-    Sphere mirrorSolid(
+    // solid : create sphere at origin, with specified angular limits;
+    // phi limits are increased to fill gaps (overlaps are cut away later)
+    Sphere mirrorSolid1(
         mirrorRadius,
         mirrorRadius + mirrorThickness,
         mirrorTheta1,
         mirrorTheta2,
-        -mirrorPhiw/2.0,
-        mirrorPhiw/2.0
+        -40*degree,
+        40*degree
         );
-    Volume mirrorVol(detName+"_mirror_"+secName, mirrorSolid, mirrorMat);
-    mirrorVol.setVisAttributes(mirrorVis);
 
-    // placement (note: transformations are in reverse order)
+    // mirror placement transformation (note: transformations are in reverse order)
     auto mirrorPos = Position(mirrorCenterX, 0., mirrorCenterZ) + originFront;
-    auto mirrorPV = gasvolVol.placeVolume(mirrorVol,
+    Transform3D mirrorPlacement(
+          Translation3D(mirrorPos.x(), mirrorPos.y(), mirrorPos.z()) // re-center to specified position
+        * RotationY(-mirrorThetaRot) // rotate about vertical axis, to be within vessel radial walls
+        );
+
+    // cut overlaps with other sectors using "pie slice" wedges, to the extent specified
+    // by `mirrorPhiw`
+    Tube pieSlice( 0.01*cm, vesselRmax2, tankLength/2.0, -mirrorPhiw/2.0, mirrorPhiw/2.0);
+    IntersectionSolid mirrorSolid2( pieSlice, mirrorSolid1, mirrorPlacement );
+
+    // mirror volume, attributes, and placement
+    Volume mirrorVol(detName+"_mirror_"+secName, mirrorSolid2, mirrorMat);
+    mirrorVol.setVisAttributes(mirrorVis);
+    auto mirrorPV2 = gasvolVol.placeVolume(mirrorVol,
           RotationZ(sectorRotation) // rotate about beam axis to sector
-        * Translation3D(mirrorPos.x(), mirrorPos.y(), mirrorPos.z()) // re-center to specified position
-        * RotationY(-mirrorThetaRot) // rotate about origin
+        * Translation3D(0,0,0)
         );
 
     // properties
     DetElement mirrorDE(det, Form("mirror_de%d", isec), isec);
-    mirrorDE.setPlacement(mirrorPV);
+    mirrorDE.setPlacement(mirrorPV2);
     SkinSurface mirrorSkin(desc, mirrorDE, Form("mirror_optical_surface%d", isec), mirrorSurf, mirrorVol);
     mirrorSkin.isValid();